We use cookies to allow us and selected partners to improve your experience and our advertising. By continuing to browse you consent to our use of cookies. You can understand more and change your cookies preferences here.


When you click on a retailer link on our site, we may earn affiliate commission to help fund our not-for-profit mission.Find out more.

15 Sep 2021

Do you have a safe and reliable carbon monoxide alarm in your home?

More than 20% of UK homes are without carbon monoxide alarms.

New Which? research reveals that one in five UK homes are without a carbon monoxide (CO) alarm and won't be protected from the killer gas in the event of a CO build-up.

With high levels of the deadly gas having the potential to kill in minutes, the consequences of not being alerted about the presence of CO don't bear thinking about.

And with Which? research proving repeatedly that some dangerously unresponsive CO alarms are just as bad as not having an alarm fitted at all, Gas Safety Week 2021 is an excellent reminder to make sure you have a reliable and responsive CO alarm fitted in your home.

So, here we show you the CO alarms to avoid, why you need a CO alarm, the signs of CO poisoning to look for and how to find a reliable CO alarm for your home.

If you just need to find the best carbon monoxide alarm for your home, head straight to our CO alarm reviews.

Why you need a carbon monoxide (CO) alarm

Carbon monoxide is colourless and odourless. So, if a fuel burning appliance is releasing the deadly gas, you'll not be able to smell it or see it.

Carbon monoxide alarms are designed to sound when the concentrations of CO in the air are enough to harm you. A good CO alarm will sound when it detects the gas and it will be loud enough to alert everybody in the house.

A CO alarm will sound when there are 50 or more parts per million (PPM) of CO in the air and alarms are designed to sound more quickly when higher and more dangerous concentrations of the gas.

When you hear a CO alarm sound, get everybody in your home out as quickly as you can and call 999.

When test whether CO alarms can detect the presence of CO more than 30 times for each brand. Only those that sound the alarm every time CO is present become Best Buys.

Tips for living well - get our free Food & Health newsletter: shop savvy, eat well, stay healthy

Who needs a carbon monoxide (CO) alarm?

If you have an appliance that burns fuel in your home, such as a gas, LPG, oil or wood boiler, you'll need a carbon monoxide alarm in every room that fuel is burned in.

Also, install a CO alarm if you have a wood or coal burning fire or a wood burner.

In May and June 2021, we asked 7,125 members of the public who owned a fuel-burning appliance whether they had a CO alarm. Concerningly, 20% didn't have a CO alarm, and 2% didn't know.

Carbon monoxide (CO) poisoning symptoms to look for

Check out the signs of exposure to carbon monoxide, both at low and high levels of the gas.

Low level exposure to carbon monoxide

Headaches are the most common symptom of mild carbon monoxide (CO) poisoning.

Other symptoms associated with CO poisoning include dizziness, feeling sick and vomiting, confusion and tiredness, stomach aches, shortness of breath and difficulty breathing.

Low level exposure to CO can feel like food poisoning or the flu without a high temperature.

If you're exposed to CO at low levels for a long period of time, concentration may become difficult and you may experience frequent mood changes.

High level exposure to carbon monoxide

Inhaling high concentrations of CO can produce more severe symptoms including intoxication, vertigo, loss of co-ordination, breathlessness, tachycardia, chest pains, seizures and unconsciousness.

In the worst cases, breathing high concentrations of carbon monoxide can lead to death in minutes.

Pets, children and the early signs of carbon monoxide (CO) poisoning

Pets and also children can be the first to show signs of carbon monoxide (CO) poisoning.

This is because they both have smaller lung capacities than adults and because of this, they're more sensitive to high levels of the gas and can be affected more quickly.

Pets can also be more at risk of carbon monoxide poisoning based on them being left in the same room as appliance that's producing CO, such as a faulty boiler in a kitchen

Small pets, such as birds, can be particularly badly affected by a CO build-up.

How to spot a dangerous carbon monoxide (CO) alarm

Don't buy carbon monoxide (CO) alarms costing less than £10. Cheap and unbranded CO alarms, including all of those featured above, tend to do a terrifyingly poor job of detecting the deadly gas. So, expect to pay around £20 for a CO alarm.

Buy an alarm from a well known brand. The CO alarms that regularly fail to detect CO in our tests are almost exclusively unbranded products that are typically only available through online marketplaces.

Well known brands of alarm that you will see on the high street pass all of our carbon monoxide detection tests typically.

These Don't Buy carbon monoxide alarms are the ones to avoid.

How to find a carbon monoxide (CO) alarm that you can rely on

Buy an alarm from a well known brand and look for accreditation marks, such as the Kitemark, that show the alarm has passed standard CO detection tests.

But we've found alarms from well known brands that have failed to sound when tested. So, find an alarm that responds every time by checking out our Best Buy carbon monoxide alarms.

Why you should go with a Gas Safe registered engineer?

Choosing a Gas Safe Registered engineer is your only route to have gas appliances fitted, installed, removed and repaired legally and safely.

Gas engineers need to be licensed by Gas Safe Register in order to legally work with gas in the UK. To gain registration, engineers need to hold a current and valid gas competence qualification.

Use Which? Trusted Trader to find a gas engineer

If you're looking for someone to come and fit a new boiler or gas fire for you or you need an engineer to service a fuel-burning appliance, head over to Which? Trusted Traders to find a Gas Safe Registered engineer you can trust who has been checked-out by Which?.

Before allowing traders to join the Which? Trusted Trader scheme, we check applicants' credit reports, we find out how happy their customers are with the work they've carried out and we examine how they run their businesses.

And trading standards experts from Which? carry out face-to-face interviews with anyone applying to join

Go to Which? Trusted Traders to find a Gas Safe Registered engineer local to you.

Find out how an annual boiler service could save your life by checking for issues that could lead to a CO leak.